Patent GB-711250-A (GB)
Title: Improvements in turning gear for steam turbines
Inventor: TOWLE EDWARD LOUIS NEVILLE
IPC: F01D25/34
Filed: 1952-05-28
Abstract: 711,250. Turning-gear. METROPOLITAN-VICKERS ELECTRICAL CO., Ltd. May 8, 1953 [May 28, 1952], No. 13577/52. Class 7(5) in turning gear for steam turbines comprising a clutch 3, 4, Fig. 1, for operatively connecting the turbine rotor with power means, not shown, a servomotor 5 for actuating the clutch, a manually displaceable member, such as lever 10, for controlling the servomotor 5, and a detector device 11 which is responsive to rotation of the turbine shaft and is operatively associated with the lever 10, the detector device prevents displacement of the lever by an amount sufficient to cause the clutch to engage when the turbine is in motion but allows engagement of the clutch when the turbine is stationary. Arrangement. The electric starting motor (not shown) drives the turbine through a worm or spur reduction gearing the final wheel 1 of which is splined upon an axially-slidable shaft 2 that carries toothed clutch-member 3, the co-operating clutch-member 4 being mounted upon or connected by reduction gearing to the turbine shaft. Operation of the clutch is effected by the double-acting fluid-operated servomotor 5, through a piston rod 5a and a lever 6 whilst the admission of fluid to the motor is controlled by valves 7 and an electrically-atcuated master-valve 8. Valve 8 is controlled by a limit switch 9 which is operated by lever 10 through linkage 10a 10b, the latter being connected to the detector device 11 and a lock 12 in the rod 5a; member 10a is provided with a pawl and ratchet gear 13. Operation. The initial movement of the lever 10 in the direction of the arrow lowers the detector device 11 on to the turbine shaft or the first reduction-shaft connected thereto and if the shaft is revolving the lever 10 will be prevented from completing more than one-third of its total movement thereby preventing both withdrawal of the lock 12 and closure of switch 9; however the ratchet gear 13 becomes effective to prevent opening but not closing of "ahead" and "astern" manoeuvring valves (not shown). If the shaft is stationary the movement of the lever 10 can be completed so withdrawing the lock 12 and closing switch 9 to energize valve 8 and cause the servomotor 5 to engage the clutch 3, 4; immediately prior to the latter action another limit switch 14 is closed by lever 6 to energize an automatic starter (not shown), and so apply a low torque to the starting motor so that in the event of the abutment of the clutch teeth the slow turning of member 3 will facilitate indexing. Upon moving lever 10 into the position shown the switches 9 and 14 are opened with consequent disengagement of the clutch and de-energization of the starting motor; at the same time the manouvring valves are freed for opening by release of gear 13. The manoeuvring valves cannot be freed when the clutch is engaged or there is a failure in the fluid system of servomotor 5. Rotation detecting device. The piston 16, Fig. 2, is reciprocated by an element 17 on a crank 18 which is connected to member 10a, Fig. 1, the piston incorporating a pin 20, Fig. 2, that supports a bolt 21 with a slot 22 through its head for the pin. When the piston 16 is depressed a shoe 26 and the bolt makes contact with the shaft 27, which, if it is revolving, moves the bolt to the left or right, depending upon the direction of shaft rotation, away from the central position so that a shoulder 23 on the bolt engages with. the lower piston edge and prevents further movement of the piston and hence of lever 10. If the shaft is stationary the bolt can enter a recess 24 in the piston and permit a complete starting movement of lever 10. In a modification, a multi-sided cam on the shaft operates, during rotation of the latter, a plunger in a hydraulic dashpot movable by the starting lever into engagement with the cam; reciprocation of the plunger causes liquid to be forced through a non- return valve and into a cylinder to act upon a piston which maintains closed a valve that controls the flow of liquid to the master-valve. All the pipes are flexible. In another modification, a cam operates an electrical contact-making device in a delayed-response circuit so that if the circuit is made and broken at intervals a relay over which the master-valve is energized is prevented from closing.